I think I squashed the last 40 commits using rebase.
I was following this guide to make sure I didn\'t do anything stupid - http://gitready.com/advanced/2009/02/10/squashing
If the rebase "todo list" couldn't be saved, your rebase didn't work.
The easiest way to squash that many commits would be to do git reset --soft HEAD~40 and then git commit with your new message - assuming you want to squash all of them.